This invention relates to tubes and their manufacture, particularly flat tubes primarily intended for use in heat exchangers.
Flat heat exchanger tubes are often used in heat exchangers for use in automotive vehicles, to carry a first fluid, a second fluid being maintained in heat exchange relationship with the exterior of the tube so that heat is transferred between the first and second fluids.
It is known to manufacture flat heat exchanger tubes by a cold-rolling process from coated aluminium strip, the coating providing a xe2x80x9cbrazingxe2x80x9d medium for sealing and securing abutting walls of the tube, and sometimes also for securing the tube to other components of the heat exchanger matrix when the heat exchanger is first manufactured.
Flat heat exchange tubes are, in lateral cross-section, relatively wide and shallow having planar, parallel, upper and lower walls interconnected by integral curved side walls. It is known to form such a tube by rolling elongate aluminium strip to raise and bend inwardly the opposite lateral edge regions of the strip to form the upper wall of the tube. The lateral edge regions engage one another at the longitudinally extending mid-line of the upper wall, and it is known from, for example, European patent 0302232, to bend the free edges of the lateral edge regions inwardly so as to lie within the tube and to define a partition within the tube extending between the upper and lower walls of the tube.
In accordance with the present invention there is provided a flat heat exchanger tube formed by rolling metal strip to fold inwardly the lateral edge regions of the strip to provide a tube having parallel, spaced, generally planar upper and lower walls, one of said lateral edge regions being bent to define a longitudinally extending partition wall extending within the tube towards said lower wall, said partition wall including first and second longitudinally extending regions disposed at an angle to one another so as to provide in one face of the partition wall a longitudinally extending recess receiving the free edge portion of the other of said lateral edge regions of the strip.
Preferably said partition wall contacts the inner surface of said lower wall and said free edge portion of said other of said lateral edge regions of the strip terminates within said recess of the partition wall.
Preferably said first region of said partition wall extends inwardly of the tube from said upper wall generally at right angles to said upper wall, said second region commences at the inner edge of tile first region and extends at an oblique angle to said first region, and, said partition wall includes a third region integral with said second region and commencing at the edge of the second region remote from the first region, said third region extending from said second region to contact the inner surface of the lower wall and lying parallel to said first region but in a plane spaced from the plane of the first region.
Conveniently the angle and extent of said second region, relative to said first and third regions, is such that said third region plane is spaced from said first region plane by the thickness of the strip material.
Desirably, the partition wall includes a fourth region commencing at the edge of the third region remote from the second region, said fourth region being a region of the strip bent through 180xc2x0, and thus lying in facial contact with the face of the partition wall remote from the face of the partition wall engaged by said free edge portion of said other of said lateral edge regions of the strip.
Alternatively said second region extends at right angles to said first region, and conveniently said third region terminates in an integral fourth region extending at right angles to said third region and ill facial contact with the lower wall of the tube.
Alternatively said first region of said partition wall extends inwardly from said upper wall of the tube at an acute angle to said upper wall, and said second region extends at an obtuse angle to said first region so as to contact the inner surface of said lower wall of the tube generally opposite the root of said first region at the upper wall.